[LTS] v1.3.0 maintenance update

Note

MGPP (≥v1.3.0, <2.0.0) is under maintenance mode, no further feature updates.

Changes

• Fixed bug: Running runClient and runServer tasks failed on gradle 8.0+.
• Feature: Downloaded games file from GitHub will be put under $GRADLE_USER_HOME/mindustry-mgpp/games.
• Feature: Symbolic link of downloaded game files will be created under build/tmp/downloadClient and build/tmp/downloadServer.